Abstract

This thesis operates at two levels of ecological research, describing the effects of withdrawal and
re-introduction of management on grasslands. The aim of the community-level survey was to explore the effects of
abandonment, mowing and grazing on semi-natural meadows in northern Finland. At the species level, the aim was to
evaluate the responses of three monocarpic meadow species to various degrees of simulated grazing under natural growth
conditions.

The community-level studies suggest that strongly competitive grass species with rapid vegetative
growth, especially those forming tussocks, are able to retain or increase their cover in abandoned meadows. However,
most species are able to persist in a meadow for a long time after abandonment, even when a group of immigrants arrive.
This leads to a temporary increase in species diversity, and it may therefore be used as an indicator of ongoing
succession. Nevertheless, abandonment is harmful for the rare archaeophytic species in the long run. Late mowing does
not have extensive short-term impacts on grass-dominated semi-natural meadows. Therefore, it is neither an efficient nor
a substitutional way of management when the goal is to restore a formerly grazed pasture. Mowing executed early in the
season may, however, be a more appropriate way of inducing changes in species composition and enhancing species
richness.

According to the results of the species-level studies, Erysimum strictum and
Rhinanthus minor tolerate well minor apical damage, while more severe damage has a detrimental
impact on the performance of both species. The observed differences in regrowth responses between the two species are
presumably due to their different habitat requirements in relation to competition. The species-level experiment with two
late-flowering populations of field gentian Gentianella campestris ssp.
campestris revealed that the southern, Swedish population that has been regularly grazed and mown
overcompensated for the intermediate (50%) damage level, whereas the northern, Finnish field gentians growing in
unmanaged habitats showed at best partial or full compensation. Regular grazing and mowing have presumably favoured
grazing-tolerant plant species, i.e. species with a good regrowth capacity.

Herbivory reshapes grassland plant communities in two ways: directly by affecting the survival and
reproductive success of individual plants and indirectly by changing the competitive environment. Tall and competitive
perennial species suffer relatively more from damage than true grassland species, i.e. small herbs and grasses, which
are better able to tolerate regular tissue losses and respond to damage within the ongoing growing season. As a result,
certain species benefit from grazing and mowing in the sense that they may gain more through competitive relaxation than
they lose in defoliation.